Pneumatic tires

ABSTRACT

Radial ply tires having good vertical flexibility as well as lateral stability even at high speeds are disclosed. The tires are characterized by a sidewall construction in which a radially inward zone in at least one sidewall is reinforced only by the ply structure of the radial carcass itself, and the respective adjacent radially outwardmost sidewall zone contiguous with the tread region of the tire is additionally reinforced by a supplementary ply structure of the carcass extending from the breaker region into the sidewall. In a preferred embodiment, the supplementary ply structure comprises sheet material folded back upon itself, with the folded edge defining the boundary between said sidewall zones. As a refinement of the invention, the respective adjacent radially inwardmost zone of the same sidewall contiguous with the associated bead region is also additionally reinforced by an extended bead turnup section folded back upon itself. The resultant intermediate sidewall zone of limited reinforcement, bounded by the proximate edges of the additional reinforcing plies in the two other zones, is of considerably reduced width with respect to the normal width of a sidewall between the proximate edges of the standard breaker and bead turnup, whereby the tire is somewhat rigidified but retains an optimum degree of flexibility. The sidewall region corresponding to the intermediate zone may also be reduced in thickness.

v United States Patent [72] Inventors Henri Mirtain and Andr Devienne,Compiegne. France 211 Appl. No. 745,278

[22] Filed July 16, 1968 [45] Patented Jan; 12, 1971 [73] AssigneeUniroyal Englebert France S. A. Paris, France a corporation of France [32] Priority July 24, 1967 [3 3] France [54] PNEUMATIC TIRES 15 Claims,14 Drawing Figs.

- Primary ExaminerJames B. Marbert Attorney-Norbert P. Holler ABSTRACT:Radial ply tires having good vertical flexibility as well as lateralstability even at high speeds are disclosed. The tires are characterizedby a sidewall constniction in which a radially inward zone in at leastone sidewall is reinforced only by the ply structure of the radialcarcass itself, and the respective adjacent radially outwardmostsidewall zone contiguous with the tread region of the tire isadditionally reinforced by a supplementary ply structure of the carcassextending from the breaker region into the sidewall. In a preferredembodiment, the supplementary ply structure comprises sheet materialfolded back upon itself, with the folded edge defining the boundarybetween said sidewall zones. As a refinement of the invention, therespective adjacent radially inwardmost zone of the same sidewallcontiguous with the associated bead region is also additionallyreinforced by an extended bead tumup section folded back upon itself.The resultant intermediate sidewall zone of limited reinforcement,bounded by the proximate edges of the additional reinforcing plies inthe two other zones, is of considerably reduced width with respect tothe normal width of a sidewall between the proximate edges of thestandard breaker and bead tumup, whereby the tire is somewhat rigidifiedbut retains an optimum degree of flexibility. The sidewall regioncorresponding to the intermediate zone may also be reduced in thickness.

PATENTEU JA'N i 212m SHEET 2 BF 4 I N VEN T( )RS PATENTEDJANIZIBH I3.554.261

sum 3 OF 4 BYWRM PATENTED JAN l 2mm 3,554, 51

- sum u or 4 l N VEN TORS Maw/1.2a

to the following detailed description and the accompanying.

drawings as well as to the claims.

This invention relates to pneumatic tires for vehicles, and moreparticularly to the typeof tires generally called radialor radial plytires.

. The expressions radial tires and radial ply tires" as commonly used inthe pneumatic tire art may be said to include various tire constructionshaving one or more body or carcass reinforcement plies of weftless cordfabric extending from bead to bead wherein the cords or cables in eachply are substantially radial in orientation. Specifically, in a monopolyradialtire construction, the cords or cables normally haveta high biasangle of 90, i.e. in the unshaped carcass they aredisposed perpendicularto the planes of the beads, andin the finished tire in meridian orradial planes of the same which are perpendicular to the equatorial orcircumferential center plane of the tire. In a two-ply radial tireconstruction, the

cords or cables inthe two body plies are usuallyoriented at respectiveoppositely disposed small angles of up to to the perpendicular to theequatorial plane, in which case the respective body plies are said tohave oppositely disposed high bias angles of 80 or greater (but lessthan 90). In four-ply or heavier radial tire constructions, similaropposed orientation of the cords in successive body plies is usuallyemployed. All of these body or carcass constructions are contemplatedwithin the scope and-meaningof the expressions radial, andsubstantiallyradiaP as used herein. I

Radial tires also generally have a breaker or belt interposed betweenthe crown region of the carcassand the tread for reinforcing the latter,such breaker being comprised of one or more plies of usually weftlesscord fabric the cords or cables of which are made ofgenerallyinextensible materials, e.g. metallic wires, glass filaments,polyester filaments, etc. In a monopoly breaker, the cords or cableshave a relatively low bias angle of 0, i.e. they are orientedsubstantially parallel to the planes of the beads and the equatorialplane or crowncen: terline of the tire. Ifthe breaker is a multiplystructure, similar but opposed low bias orientations of the cords orcables generally at angles ranging up to about 25 or so with respect tothe equatorial plane are employed in successive plies.

In respect of radial ply tires, furthermore, it is well known that therelatively thin,sidewalls of such tires, i.e. the zones between thebreaker and the beads, are characterized by relatively high flexibility,both transversely and vertically, because the cables or the cords of thebody ply or plies are disposed in the meridian or radial planes of thetire.-On the other hand, the breaker and bead zones of the tire are muchmore rigid and afford a greater resistance to the stresses which tend todeform them, particularly in the transverse direction. The fact that thesidewall zones are vertically flexible is rather advantageous, in thatthis flexibility improves the general riding comfort of the vehicle onwhich such tires are mounted. Because of their transverse flexibility,however, the ordinary radial ply tires have a tendency to impart to thevehicle lateral rocking or yawing movements which give the driver afloating" sensation. Especially, at high speeds this sensation is yetanother modifiedsidewall construction according to the particularlydisagreeable, because it becomes more and more difiicult to control thevehicle as the speed increases. This phenomenon can probably. beattributed to too weak a rigidity of the sidewalls, and the proof ofthis is that standard bias ply flexibility in the vertical plane,eliminates the undesirable lateral reactions.

Accordingly, it is a more specific object of the present invention toprovide a radial tire having more rigid than usual sidewalls which arealso characterized by a zone reinforced only by the radial ply alone soas to retain some flexibility.

The objectives of the present invention are basically achieved by theincorporation, in such a radial tire,.of at least one additional ply forthe radial carcass in the crown region or breaker zone thereof, such plyor plies extending into the radially outermost or upper zone of at-leastone of the sidewalls and adhering both to the inner ply of the breakerand to the radial carcass. A further refinement of the invention entailsthe extension of the bead tumup portions of theradial ply to asubstantial degree toward the said upper zone so as to provide anoptimum width of an intermediate zone reinforced only by the main ply orplies of the radial carcass itself. Preferably, in the upper and lowersidewall zones, the additional ply orplies and the turnups,respectively, are folded back on themselves so that the possibility ofply separation at the boundaries of the intem-rediate sidewall zone issubstantially minimized. If desired, the thickness of the sidewall overthe expanse of the said intermediate zone of the casing may also bereduced.

The foregoing and other objects, characteristics and advantages of thepresent invention will :be more clearly understood from the followingdetailed description thereof when read in conjunction. with theaccompanying drawings, in'

which:

FIG. I is a radial section through a standard radial ply tire with acontinuous carcass;

FIG. 2 is a similar sectional view of a radial tire having a sidewallconstruction according to the present invention FIGS. 3 and ,4 aresimilar views showing modifications of the tire sidewall constructionsaccording to the present invention;

FIGS. 5 and 6 are similar but fragmentary sectional views of such tiresandshow other possible arrangements of the rein forcements in the uppersidewall zones of tires according to the present invention;

FIGS. 7 and 8 are similar but fragmentary sectional views of such tiresand show other possible arrangements of the reinforcements in the lowersidewall zones of tires according to the present invention;

FIG. 9 is a radial sectionthrougha standard radial ply tire with adiscontinuous carcass;

FIGS. 10 and 11 are similar views of radial tires with a discontinuousradial carcass having sidewall constructions according to the presentinvention;

FIGS. 12 and 13 are similar. but fragmentary views of modifications ofthe structures shown in FIGS. 10 andll; and

FIG. 14 is aradial sectionthrough a radial ply tire having presentinvention.

Referring now to the drawings in greater detail, the tire 20 shown inFIG. I is of the most usual type and comprises sidewalls 21 and 22terminating at their radially inwardmost ends in beads 23 and 24 andmerging at their radiallyoutwardmost ends intoa tread 25 defining theroad-contacting surface of the tire. In this tire, the carcass or bodyof the tire isshown as a continuous radial ply structure 26 the oppositeend regionsof which are turned up around the bead wire bundles orcores27and 28 and, asshown at'26a and 26b,.extendforashort distance outwardlythrough the sidewalls 21 and 22.A'- breaker structure 29, generallycoextensive with the tread 25 and extending from one tire shoulder tothe other, as shown at 29a and 29b, is interposed. between the. crownregion of thecarcass 26 and the tread-'25 to reinforce the latter. It.will be understood that either the carcass or thebreakerstructureorboth'of them may be of eithermonopoly or multiply construe-- tion, andthat the cord or cable elements thereof may bemade of any suitablenatural or synthetic fibers such as nylon, rayon,

polyester, metal wire, glass fiber, etc.

In a tire of this type, therefore, the sidewalls 21 and22' arereinforced only by the radial ply carcass 26 itself over substantiallythe entire radial heightA of the tire.-Actually, of course,-

the bead tumup portions 260 and 26b of the carcass aflord some extrareinforcement to a relatively small zone of the sidewalls in the regionof the beads 23 and 24, so that the effective height B of minimumreinforcement is somewhat smaller, but the width of this zone is for allpractical purposes insufficient to achieve any appreciable reduction inthe flexibility of the sidewalls.

To attain the basic objective of the present invention, i.e. to bringabout an appropriate increase in the rigidity of the sidewalls whichwill be sufficient to enhance the lateral stability of the tire but notto affect the softness of the ride adversely to a marked degree, thetire 20a according to the embodiment of FIG. 2 comprises, in addition tothe aforesaid conventional elements, an extra reinforcing ply 30overlying the carcass 26 in the breaker or crown zone and extendinglaterally therebeyond for a considerable distance into the radiallyoutermost or upper parts of the sidewalls 21 and 22, terminating inedges 30a and 30b so as to provide an additionally reinforced sidewallzone S. As will be understood, the extra ply 6 also includes cables orcords made of a natural or synthetic fiber such as, for example, nylon,rayon, polyester, etc., these cords or cables, however, being orientedat an angle of between and 60 to the median equatorial plane x-x of thetire.

The effect of the provision of the additionally reinforced zone S,therefore, is to reduce the width of that zone of the sidewalls the solereinforcement of which is the radial ply carcass, from the values A andB (as in the ordinary radial tires) to the value C, the arrangementpreferably being such that C is equal to about one-half B or aboutone-third A. Even such tires, without more, tend to reduce lateralinstability of the vehicle to a large degree, because of the overalllower lateral flexibility of the sidewalls, and, consequently,contribute to a much better behavior of the vehicle onthe road.

This behavior may, in accordance with other aspects of the presentinvention, be improved still further, in the first instance byreinforcing the upper sidewall zone S more than is achieved by the ply30, and then by simultaneously additionally reinforcing a lower butnoncontiguous sidewall zone. Thus, as shown for the tire 20b in FIG. 3,the desired added reinforcement of each of the sidewall zones S isprovided by doubling the thickness of the extra reinforcing ply 30 insaid zones, as indicated at 31 and 32, preferably by folding itsmarginal regions back on itself in such a way that the edges 31a and 32aare located in the immediate vicinity of the respective side edges 29aand 29b of the breaker structure 29. This arrangement also has theadvantage that the folded-over edges 33 and 34 of the ply 30 tend toprotect the tire against ply separations which otherwise might possiblyoccur in service.

The added reinforcement of the upper sidewall zones achieved in FIG. 3by folding the ply 30 back over itself may, of course, be effected indifferent ways, depending on the nature of the stresses which the tirecasing is intended to undergo in service. Thus, as shown for the tire20c in FIG. 4, the folded-back parts 31 and 32 of the ply 30 may beextended in under the breaker 29 so as to dispose their edges 31b and32b either in the vicinity of the median equatorial plane x-x of thetire, or at any desired one of the positions between those shown inFIGS. 3 and 4. Alternatively, as shown for the tires 20d and 20e inFIGS. and 6, the same effect can be achieved by using, in lieu of asingle sheet of material to form the double ply projecting out into theupper sidewall zones, two folded sheets such as 35 and 36 the respectivepairs of ends 35a35b and 36a36b of which may be disposed under thebreaker either in or out of registry with one another.

It should be noted that where the reinforcement of the upper sidewallzones is effected by the use of two folded-back double ply-formingsheets 35 and 36, these need not necessarily be arranged symmetricallywith respect to the median equatorial plane of the tire. In fact, incertain cases, e.g. should an asymmetric tire construction be desired,one of these ply structures may even be eliminated.

Although, as previously indicated, the use of radial tires only theupper sidewall zones of which are additionally reinforced by any of theabove-mentioned means, contributes to a better road behavior of avehicle equipped with such tires, this behavior may, if necessary beimproved still more by additionally reinforcing the lower or radiallyinwardmost sidewall zone I, as shown merely by way of example in FIG. 4.Such a reinforcement is advantageously obtained in a simple manner byproviding longer than usual bead turnup portions 37 and 38 for thecarcass 26 and folding each of these back on itself, for example towardthe inside of the casing, in such a way that the interior layers 37a and38a of the folds terminate close to the bead cores 27 and 28, asindicated at 37b and 38b. The extent to which the end regions of the ply26 are thus folded back should be such that the distance from each ofthe folded edges 37c and 38c to the corresponding bead core is greaterthan the distance (approximately A minus B in FIG. 1) which, in anordinary casing, separates the bead turnup edges 26a and 26b from thecorresponding bead cores.

It will be appreciated, therefore, that by such a construction the lowersidewall zone I of the tire is provided with an extra reinforcementwhich considerably rigidities it, while at the same time the width D ofthe intermediate sidewall zone M, i.e. the zone in which the onlyreinforcement for the sidewalls is afforded by the radial ply carcassitself, is so reduced as to be markedly less than even the alreadyreduced width C of the comparably reinforced sidewall zones in the tiresaccording to the embodiments of the invention illustrated in FIGS. 2 and3. Nevertheless, the intermediate sidewall zone M is made sufficientlywide to retain an optimum degree of the initial flexibility of thesidewalls so as to maintain as much of the soft riding qualities of thetires as possible under the circumstances. As before, of course, theprovision of folded edges at the boundaries of the upper and lowersidewall zone extra reinforcing plies between which the intermediatezone is defined, has the additional advantage of preventing possible plyseparations which might otherwise occur in service.

It will be apparent that the lower zone extra reinforcement effect maybe achieved as well by folding the bead tumups toward the outside of thecasing rather than toward the inside, as shown at 38d and 38e in FIGS. 7and 8, respectively. Moreover, the outside layers may extend either theentire distance E separating the fold of the ply from the base of thecorresponding bead, as shown in FIG. 7, or only a part F of thisdistance, for example one-half E, as shown in FIG. 8.

As in the case of the upper sidewall zone reinforcement, the extrareinforcement of the lower sidewall zone I may be provided in only asingle sidewall and in any one of the different ways described, andwhere it is provided on both sidewalls at the same time, this may bedone in different ways, for example by different widths of the outsidelayers of the bead tumups in the different sidewalls.

In accordance with the principles of the present invention, therefore,the extra reinforcement of the upper sidewall zones S and the lowersidewall zones I may be achieved in appropriately predetermined ways byany of the different modifications disclosed herein, which, of course,may be taken in all their technically attainable combinations dependingon the desired characteristics of the tire casing according to the invention to be produced.

Referring now to FIG. 9, there are presently known certain equallycommon types of radial ply tires 20 having a discontinuous carcasscomposed of two radial sections 26' and 26", each of these being turnedup at one edge region around a respective bead core 27 or 28 andterminating at its other edge region under the breaker 29 of the tire,where the last-named edge regions of the ply sections may or may not beoverlapped.

For tires of this class, the extra reinforcement of the upper sidewallzone S is achieved, in accordance with one aspect of the invention asshown for the tire 20f in FIG. 10, by the provision of an internalreinforcing ply 39 in the crown region of the carcass in bridgingrelation to the discontinuity between the ply sections. As in the caseof the ply 30 (FIG. 2), the ply 39 extends beyond the lateral edges ofthe breaker 29 into the sidewalls 21 and 22, terminating at 39a and 3%so as to leave a sidewall portion of width, i.e. radial height, Creinforced only by the radial carcass itself. The cord structure andorientation of the ply 39 likewise are the same as those of the ply 30described above. I

If desired, the extra reinforcement may be supplemented 'by vicinity ofthe corresponding ends 39a and 39b of the ply 39.

The ply 40 may, if desired or necessary, be folded back on itself in thefashion of the ply 32 shown in FIG. 3. Furthermore, and without anyadverse effect on the reinforcement desired; either one of the two plies39 and 40 may, for example as a possible convenience in building thecarcass, be constructed as a discontinuous ply by being built 'of twoseparate ply sections, such as 41 and 42 shown for the tire h in FIG.'12, or 43 and 44 shown for the tire 201 in FIG. 13. i

In the discontinuous carcass types of tires, as before, the ad ditionalreinforcing plies for the upper sidewall zones need not be symmetrical.Thus, the extra reinforcement may -.be provided on only one sidewall, orelse be more accentuated on one sidewall than on the other, or even inrespective sidewall zones which may not be the same on each side'of'thetire. Likewise all the modifications of the extra reinforcement of theupper sidewall zones of these discontinuous radialply carcass tires maybe combined with any of the modifications of the extra reinforcement ofthe lower sidewall zones described previously and illustrated in FIGS.4, 7 and 8, so as to provide an intermediate sidewall zoneM ofappropriate height, depending on the desired structural and operatingcharacteristics desired for the tires being produced.

Referring now to FIG. 14, the tire 20j there shown is essentially thesame as the tire 200 (FIG. 4), with the'upper and lower sidewall zonesbeing additionally reinforced by the extra reinforcing plies 30-31-32and 37/37a--38/38a, respectively. The tires'differ from one another onlyin that the sidewalls 21 and 22' of the tire 20 are specially molded,during the curing operation, to have generally central portions45 thatone of the radially inwardmost'sidewall zones on the'sanie It will beunderstood that the-foregoing description of preferred embodiments ofthe present invention-is for purposes of illustration only, and that thevarious structural features and relationships herein disclosed aresusceptibleto a tially coextensive in width with said tread interposedbetween. said carcass and said tread for reinforcing thelatter, and.-sidewalls overlying the lateral portions of said carcass from said treadto said beads; the improvement comprising asupplementary tire cord plystructure built into said carcass at least partly under said breaker andextending laterally from" said crown region of said carcassinto theradially outwardmost zone of at least one of said sidewalls foradditionally rein-.

forcing the same, saidsupplementary'ply structure in at least said oneradially outwardmost sidewall zone being constituted by at least onesingle sheet of tire cord material folded back upon itself, with thefolded edge defining the radially inward-. most boundary of saidradially outwardmost sidewall 'zone, the

cord elements of said supplementary ply structure being made of textilecord material and oriented at an angle between about 0 and 60 to themedian equatorial plane of the tire, a'ii d the radial width of theportion of said supplementary ply structure within the confines of saidradially outwardmost sidewall zone being sufficient to effect a markedreduction inthe expanse of the contiguous radially inward sidewall zonerein forced only by said radial ply carcass, thereby to increase thelateral stability of the tire especially at high speed while mam tainingoptimum vertical flexibility and ride softness.

-2. A pneumatic tire according to claim 1, wherein the foldedbackportion of said sheet extends back toward said breaker at leastsufficiently to dispose the free edgeof said portion under the lateraledge'region ofsaid breaker.

3. A pneumatic tire according to claim I; wherein the folded backportion of said sheet extends back toward said breaker sufficiently todispose the free edge of said portion under said breaker and in thevicinity of the crown centerline of said carcass.

4. A pneumatic tire according to claim 1, wherein said sup plementaryply structure extends into both of said radially outwardmost sidewallzones.

5. A pneumatic tire according to claim 4, wherein said supplementary plystructure is symmetric with respect to the median equatorial plane ofthe tire.

6. A pneumatic tire according to claim 4, wherein said supplementary plystructure is asymmetric with respect to the median equatorial plane ofthe tire.

7. Apneumatic tire according to claim 4," wherein said supplementary plystructure in both said radially outwardmost sidewall: zones isconstituted-by atleast one common single sheet of tire cord material theopposite marginal regions of which are folded" back uponitself, thefolded edges'defining the respective boundaries between said radiallyoutwardmost" sidewall zones and said radially inward sidewalls zones contiguous thereto.

8. A pneumatic tire according to claim 4, wherein said'sup plementaryply structure in'each of said radially outwardmost sidewall-zones isconstituted by at least one separate single sheet of tire cord materialfolded back upon itself, the folded" edges defining the respectiveboundaries between said radially I outwardmost-sidewall zones and saidradially inward sidewall zones contiguous thereto.

9. A pneumatic tire according to claim '1, wherein at least side of thetire as said one 'radially outwardmost sidewall zone is additionallyreinforced by the associated'be'ad tur'nup' por tion of said radial plycarcass, said tumup'portionbeingextended radially outwardlyfor'apredeterminedfiistance from 10.A pneumatic tireaccording to claim 9;whereih'said supplementary ply structure extends intoboth of saidradially out wardmost sidewall zones, and both of saidradiallyinwart'lmost sidewall zones are additionally reinforced by folded overhead tumup portions, the proximate folded edges 'of said 'supple'mentary ply structure and said bead 'tumupportio'nin each" sidewalldefining the boundaries of *the respectiveintr mediate sidewall zones; I

11. A pneumatic tireaccording to claim lofiwhereiiisaid supplementaryply structure in both said radially"outwardinost" sidewall' zones-isconstituted by at least'onecommon-single sheet of tire cord material theopposite marginal regions of which are folded back upon itself."

12. A pneumatic tire according to claimloiwherein said supplementaryplystructurein each of said radiallyoutward most sidewall zones isconstituted by at least one separatesim gle sheet of tire cordmaterialfolded-back upon itself.

13. A pneumatic tire accordingto claim 9, wherein-the bead.

15. A pneumatic tire according to claim 9, wherein the respectivesidewall of the tire in the region of said intermediate sidewall zone isreduced in thickness.

1. In a pneumatic tire having a radial ply carcass terminating at itsradially inwardmost ends in a pair of beads, a tread surrounding thecrown region of said carcass, a breaker substantially coextensive inwidth with said tread interposed between said carcass and said tread forreinforcing the latter, and sidewalls overlying the lateral portions ofsaid carcass from said tread to said beads; the improvement comprising asupplementary tire cord ply structure built into said carcass at leastpartly under said breaker and extending laterally from said crown regionof said carcass into the radially outwardmost zone of at least one ofsaid sidewalls for additionally reinforcing the same, said supplementaryply structure in at least said one radially outwardmost sidewall zonebeing constituted by at least one single sheet of tire cord materialfolded back upon itself, with the folded edge defining the radiallyinwardmost boundary of said radially outwardmost sidewall zone, the cordelements of said supplementary ply structurE being made of textile cordmaterial and oriented at an angle between about 0 and 60* to the medianequatorial plane of the tire, and the radial width of the portion ofsaid supplementary ply structure within the confines of said radiallyoutwardmost sidewall zone being sufficient to effect a marked reductionin the expanse of the contiguous radially inward sidewall zonereinforced only by said radial ply carcass, thereby to increase thelateral stability of the tire especially at high speed while maintainingoptimum vertical flexibility and ride softness.
 2. A pneumatic tireaccording to claim 1, wherein the folded back portion of said sheetextends back toward said breaker at least sufficiently to dispose thefree edge of said portion under the lateral edge region of said breaker.3. A pneumatic tire according to claim 1, wherein the folded backportion of said sheet extends back toward said breaker sufficiently todispose the free edge of said portion under said breaker and in thevicinity of the crown centerline of said carcass.
 4. A pneumatic tireaccording to claim 1, wherein said supplementary ply structure extendsinto both of said radially outwardmost sidewall zones.
 5. A pneumatictire according to claim 4, wherein said supplementary ply structure issymmetric with respect to the median equatorial plane of the tire.
 6. Apneumatic tire according to claim 4, wherein said supplementary plystructure is asymmetric with respect to the median equatorial plane ofthe tire.
 7. A pneumatic tire according to claim 4, wherein saidsupplementary ply structure in both said radially outwardmost sidewallzones is constituted by at least one common single sheet of tire cordmaterial the opposite marginal regions of which are folded back uponitself, the folded edges defining the respective boundaries between saidradially outwardmost sidewall zones and said radially inward sidewallszones contiguous thereto.
 8. A pneumatic tire according to claim 4,wherein said supplementary ply structure in each of said radiallyoutwardmost sidewall zones is constituted by at least one separatesingle sheet of tire cord material folded back upon itself, the foldededges defining the respective boundaries between said radiallyoutwardmost sidewall zones and said radially inward sidewall zonescontiguous thereto.
 9. A pneumatic tire according to claim 1, wherein atleast that one of the radially inwardmost sidewall zones on the sameside of the tire as said one radially outwardmost sidewall zone isadditionally reinforced by the associated bead turnup portion of saidradial ply carcass, said turnup portion being extended radiallyoutwardly for a predetermined distance from the bead core and thenfolded back upon itself to define between its folded edge and theproximate folded edge of said supplementary ply structure a reducedwidth intermediate sidewall zone reinforced only by said radial plycarcass.
 10. A pneumatic tire according to claim 9, wherein saidsupplementary ply structure extends into both of said radiallyoutwardmost sidewall zones, and both of said radially inwardmostsidewall zones are additionally reinforced by folded over bead turnupportions, the proximate folded edges of said supplementary ply structureand said bead turnup portion in each sidewall defining the boundaries ofthe respective intermediate sidewall zones.
 11. A pneumatic tireaccording to claim 10, wherein said supplementary ply structure in bothsaid radially outwardmost sidewall zones is constituted by at least onecommon single sheet of tire cord material the opposite marginal regionsof which are folded back upon itself.
 12. A pneumatic tire according toclaim 10, wherein said supplementary ply structure in each of saidradially outwardmost sidewall zones is constituted by at least oneseparate single sheet of tire cord material folded back upon itself. 13.A pneumatic tire according to claim 9, wherein the folded back part ofsaid bead turnuP portion extends back toward the associated beadsufficiently to dispose the free edge of said part in the region of thecore of said associated bead.
 14. A pneumatic tire according to claim 9,wherein the folded back part of said bead turnup portion extends onlypartly back toward the region of the core of said associated bead.
 15. Apneumatic tire according to claim 9, wherein the respective sidewall ofthe tire in the region of said intermediate sidewall zone is reduced inthickness.